1. Field of the Invention
The present invention relates to a semiconductor light emitting device having a photodetector for detecting emitted light and, more particularly, to a semiconductor light emitting device which can be suitably applied to uses requesting a high-degree light detection precision.
2. Description of the Related Art
Up to this time, in a semiconductor light emitting device for the use of an optical fiber, an optical disk, and the like, as part of the object of making the light output level of a semiconductor light emitting element assembled in the device constant, emission light of the semiconductor light emitting element was detected by a light detecting mechanism. The light detecting mechanism may have been constructed by, for example, a reflector that branches part of the emission light and a semiconductor photodetector that detects the branched emission light. In the configuration, however, the number of parts increased and, moreover, a disadvantage occurred such that the reflector and the semiconductor photodetector had to be disposed with a high precision with respect to the semiconductor light emitting element. As one of the measures for solving such a disadvantage, the semiconductor light emitting element and the semiconductor photodetector were formed integrally.
However, when the semiconductor light emitting element and the semiconductor photodetector are formed integrally, there is the possibility that the semiconductor photodetector detects not only stimulated emission light to be inherently detected but also spontaneous emission light. In such a case, the light output level of the semiconductor light emitting element measured on the basis of light detected by the semiconductor photodetector includes an error only by the amount of spontaneous emission light. Therefore, the method is also unsuitable for uses in which high-precision control on the light output level is requested.
Japanese Patent No. 2,877,785 discloses a technique of providing a control layer in a semiconductor photodetector and interrupting part of the spontaneous emission light input from a semiconductor light emitting element before the semiconductor photodetector detects it.